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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>Bulletproofing your applications with unit testing.</title>
<meta name="description" content="Bulletproofing your applications with unit testing.">
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<body>
<div class="reveal">
<div class="slides">
<section>
Bulletproofing your applications with unit testing
<img src="assets/Testing_bulletproof_vest_1923.jpg">
</section>
<section>
<h3>Confessions of a JavaScript Hitman</h3>
<img src="assets/KaoSoi-thailand.jpg" width="460"><br>
<p>I'm not a node guru (yet)</p>
<p><i>...and only I first learned JavaScript test-driven development to do this presentation!
(shhh... don't tell my next boss!)</i></p>
</section>
<section>
<h4>What we're going to cover this evening:</h4>
<p>We're going to introduce ourselves to:</p>
<ul>
<li>The test-first cycle</li>
<li>Unit testing in node</li>
<li>TDD: Test-driven development</li>
<li>BDD: Behavior-driven development</li>
<li>mocha</li>
<li>chai</li>
<li>istanbul</li>
<li>sinon (maybe)</li>
<li>rewire (maybe)</li>
<li>Async testing (doubtful, but with the mention)</li>
</ul>
</section>
<section>
<h4>What we will not cover</h4>
<ul>
<li>Alternative libraries to the ones mentioned (this ain't no shootout, Bubb!)</li>
<li>Best practices for production code (this is a down and dirty intro)</li>
</ul>
</section>
<!-- <section>
<h4>Who will benefit</h4>
<ul>
<li>Aspiring node developer (code samples VERY elementary)</li>
<li></li>
<li></li>
</ul>
</section> -->
<section>
<h4>The test-first cycle</h4>
<img src="assets/test-first-cycle.png" width="600">
<small><i>Source: Learning Behavior-driven Development with JavaScript By Enrique Amodeo (Packt) (2015)</i></small>
</section>
<section>
<h4>Test-first Cycle: key points</h4>
<ol>
<li>You should not write new code if there is no good reason to do so.</li>
<li>Use failing tests as a guide to know whether there is need for new code or .</li>
<li>We should start writing the most simple test thst will fail.</li>
<li>Simplest often starts with expecting the correct answer.</li>
<li>Run the test and watch it fail.</li>
<li>Make the test pass by writing the simplest production code possible.</li>
<li>Clean the code (refactor) if necessary after the tests pass.</li>
</ol>
<p>Rule: <i>You should only write code to fix a failing test or to write a new failing test.</i></p>
</section>
<section>
<h2>Repeat!</h2>
<p><i>...until there is no new failing test to write.</i></p>
</section>
<section>
<h4>Five rules of test-first approach</h4>
<ol>
<li>Don't write any new tests if there is not a new coding task.</li>
<li>A new test must always fail.</li>
<li>A new test should be as simple as possible.</li>
<li>Write only the minimum necessary code to fix a failing test, and don't bother with quality during this activity.</li>
<li>Only clean code when your tests pass.</li>
</ol>
</section>
<section>
<h4>Results of test-first cycle</h4>
<ul>
<li>Testable Code</li>
<li>Minimum Code</li>
<li>Easier to refactor (since you'll know if you broke anything immediately)</li>
<li>Cleaner Code (cleaning frequently)</li>
<li>Adding features is less scary since you have regression tests ready to go</li>
</ul>
</section>
<section>
<h4>Test-first Drawback</h4>
<p>You cannot adopt a test-first approach easily in a project that is in the middle of development and started without the test-first approach.</p>
<p><i>Code written without a test-first approach is often hard to test.</i></p>
</section>
<section>
<h4>TDD vs BDD</h4>
<p><small><i>Disclaimer: this is my interpretation only...</i></small></p>
<p>TDD (Test-driven development) is applying the test-first cycle to classes or components.</p>
<br>
<p>BDD (Behavior-driven development) is an extension of TDD. However, the language used and tests created focus on software features (or bugs) instead of class or component expectations. </p>
<br>
<p>BDD tests test features or bugs, not components or classes.</p>
</section>
<section>
<h4>BDD</h4>
<ol>
<li>Dan North coined the term BDD (Behavior-driven development).</li>
<li>In BDD jargon, tests are often referred to as specifications (or features).</li>
<li>Don't write new code if there is not a change in the product.</li>
<li>A change in the product always represents a feature or a bug.</li>
<li>So, our tests should test the feature or the bug.</li>
<li>Test reports should be understandable for the stakeholders (feature based).</li>
</ol>
</section>
<section>
<h4>BDD vs TDD in real world</h4>
<h1> ¯\_(ツ)_/¯</h1>
<p>We're not going to be strictly adhering to BDD today, but we will use the BDD syntax.</p>
<br>
<p>Note: when a single component represents a single feature (one-to-one) in very small systems, there is probably no point in trying to be strictly BDD.</p>
</section>
<section>
<h4>Unit Testing</h4>
<br>
<p><u><b>Unit</b></u>: a feature or a component.</p>
<br>
<p><u><b>Feature</b></u>: a single concreate action that the user can perform on the system. <br>Often a use case or user story will map to several features.</p>
<br>
<p><u><b>Component</b></u>: any software artifact, such as classes, procedures, or functions that we use to build the system.<br>Often a feature will span across multiple components.</p>
</section>
<section>
<h4>Structure of a test</h4>
<ol>
<li><b><u>Set up</u>:</b> Set up the test in a well-known state (data, input params) which allows our test to be repeatable.<br><br></li>
<li><b><u>Act</u>:</b> Perform the operation we are testing (ideally, involving a single action).<br><br></li>
<li><b><u>Assert</u>:</b> Check the return value of the operation and side effects (from other units, for example).</li>
</ol>
</section>
<section>
<h4>Mocha</h4>
<ul>
<li>Homepage: mochajs.org</li>
<li>Mocha is a JavaScript test runner and Testing Framework</li>
<li>The most popular test runner in JavaScript</li>
<li><a href="https://mochajs.org/#interfaces">Mocha BDD Interface: https://mochajs.org/#interfaces </a></li>
</ul>
</section>
<section>
<h4>Chai</h4>
<ul>
<li>Homepage: chaijs.com</li>
<li>Assertion Engine (gives us a way to check values in our unit tests)</li>
<li>Some call Chai: An expectation library</li>
<li><a href="http://chaijs.com/guide/styles/">Assertion Styles</a></li>
<li><a href="http://chaijs.com/api/bdd/">BDD API</a></li>
</ul>
</section>
<section>
<h4>Installation</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mkdir bddcalc
$ cd bddcalc
$ npm init --yes
$ sudo npm install -g mocha
$ npm install --save-dev mocha chai
$ cat package.json
</code></pre>
</section>
<section>
<h4>Run Mocha!</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
</code></pre>
</section>
<section data-transition="slide" data-background="#b5533c" data-background-transition="zoom">
<h4>Run Mocha!</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
</code></pre>
Oh noes!
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
/usr/local/lib/node_modules/mocha/lib/utils.js:634
throw new Error("cannot resolve path (or pattern) '" + path + "'");
^
Error: cannot resolve path (or pattern) 'test'
at Object.lookupFiles (/usr/local/lib/node_modules/mocha/lib/utils.js:634:15)
at /usr/local/lib/node_modules/mocha/bin/_mocha:327:30
at Array.forEach (native)
at Object.<anonymous> (/usr/local/lib/node_modules/mocha/bin/_mocha:326:6)
at Module._compile (module.js:541:32)
at Object.Module._extensions..js (module.js:550:10)
at Module.load (module.js:458:32)
at tryModuleLoad (module.js:417:12)
at Function.Module._load (module.js:409:3)
at Function.Module.runMain (module.js:575:10)
at startup (node.js:160:18)
at node.js:449:3
</code></pre>
</section>
<section>
<h4>Create your first test</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mkdir test && touch test/calc-spec.js
$ subl .
</code></pre>
<br><br>
Then edit the new test file: calc-spec.js
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
describe('Hello, Mocha', function() {
it('should fail a test', function() {
assert(false, 'true');
});
});
</code></pre>
</section>
<section>
<h4>Run Mocha</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
Hello, Mocha
1) should fail a test
0 passing (9ms)
1 failing
1) Hello, Mocha should fail a test:
AssertionError: true
+ expected - actual
-false
+true
at Context.<anonymous> (test/calc-spec.js:5:5)
</code></pre>
<br>
<br>
<p>Congrats! We've failed our first test!</p>
</section>
<section>
<h4>Let's make it pass</h4>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
describe('Hello, Mocha', function() {
it('should *NOT* fail a test', function() {
assert(true, 'true');
});
});
</code></pre>
<p>Run mocha</p>
<pre><code class="hljs" data-trim contenteditable>
$ mocha
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
Hello, Mocha
✓ should NOT fail a test
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Mocha test suites</h4>
<ul>
<li>Test suites are created by nesting our tests inside of describe() statements.</li>
<li>These describe statements can be further nested.</li>
<!-- <li>Let's create our first test suite with a pending test:</li> -->
</ul>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total');
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
- should add two numbers and return the total
0 passing (4ms)
1 pending
</code></pre>
</section>
<section>
<h4>Run the test and watch it fail</h4>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
assert.equal(result, 4, 'did not return 4');
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
1) should add two numbers and return the total
0 passing (7ms)
1 failing
1) CALCULATOR Add should add two numbers and return the total:
ReferenceError: calc is not defined
at Context.<anonymous> (test/calc-spec.js:8:20)
</code></pre>
</section>
<section>
<h4>Begin writing your production code</h4>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
var calc = {
add: function (num1, num2) {
}
};
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
assert.equal(result, 4, 'did not return 4');
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
1) should add two numbers and return the total
0 passing (8ms)
1 failing
1) CALCULATOR Add should add two numbers and return the total:
AssertionError: did not return 4
at Context.<anonymous> (test/calc-spec.js:12:14)
</code></pre>
</section>
<section>
<h4>Make the test pass by writing the simplest production code possible</h4>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
var calc = {
add: function (num1, num2) {
return num1 + num2;
}
};
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
assert.equal(result, 4, 'did not return 4');
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Clean the code</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mkdir lib && touch lib/calc.js
</code></pre>
calc.js:
<pre><code class="hljs" data-trim contenteditable>
var calc = {
add: function (num1, num2) {
return num1 + num2;
}
};
module.exports = calc;
</code></pre>
calc-spec.js:
<pre><code class="hljs" data-trim contenteditable>
var assert = require('assert');
var calc = require('../lib/calc');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
assert.equal(result, 4, 'did not return 4');
});
});
});
</code></pre>
</section>
<section>
<h4>Test again</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Repeat!</h4>
</section>
<section>
<h4>Let's talk about Chai</h4>
<p>Node's core assert module can only take us so far. Let's incorporate Chai. For starters, Chai share's an assert module that will run all of the core assert modules:</p>
<pre><code class="hljs" data-trim contenteditable>
var assert = require('chai').assert;
var calc = require('../lib/calc');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
assert.equal(result, 4, 'did not return 4');
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Chai also has more powerful 'expect' and 'should' assertion engines</h4>
<p>These allow us to more easily formulate the verbiage of our tests to read like the description of a feature test.</p>
<pre><code class="hljs" data-trim contenteditable>
var chai = require('chai'),
expect = chai.expect,
should = chai.should();
var calc = require('../lib/calc');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
result.should.equal(4);
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Choice between 'expect' and 'should' is generally a personal choice</h4>
<small>Outside of the scope of this lesson, there are some nuanced differences which result in expect() to be a more consistent approach across assertion cases.</small>
<pre><code class="hljs" data-trim contenteditable>
var chai = require('chai'),
expect = chai.expect,
should = chai.should();
var calc = require('../lib/calc');
describe('CALCULATOR', function() {
describe('Add', function() {
it('should add two numbers and return the total', function() {
var result = calc.add(1, 3);
expect(result).to.equal(4);
});
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1 passing (6ms)
</code></pre>
</section>
<section>
<h4>Add another test</h4>
<small>Watch it fail</small>
<small>calc-spec.js (partial):</small>
<pre><code class="hljs" data-trim contenteditable>
it('should throw an error if either value is not a number', function() {
var handler = function() {
calc.add('hey', 'now');
};
expect(handler).to.throw(Error);
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
1) should throw an error if either value is not a number
1 passing (11ms)
1 failing
1) CALCULATOR Add should throw an error if either value is not a number:
AssertionError: expected [Function] to throw Error
at Context.<anonymous> (test/calc-spec.js:19:31)
</code></pre>
</section>
<section>
<h4>What's next?</h4>
<small>calc.js:</small>
<pre><code class="hljs" data-trim contenteditable>
var calc = {
add: function (num1, num2) {
if (typeof num1 !== 'number' || typeof num2 !== 'number') {
throw new Error('Invalid number');
}
return num1 + num2;
}
};
module.exports = calc;
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
✓ should throw an error if either value is not a number
2 passing (7ms)
</code></pre>
</section>
<section>
<h4>Improve the test</h4>
<small>calc-spec.js (partial):</small>
<pre><code class="hljs" data-trim contenteditable>
it('should throw an error if either value is not a number', function() {
var handler = function() {
calc.add('hey', 'now');
};
expect(handler).to.throw(Error);
expect(handler).to.throw('Invalid number'); // add this line
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha
CALCULATOR
Add
✓ should add two numbers and return the total
✓ should throw an error if either value is not a number
2 passing (7ms)
</code></pre>
</section>
<section>
<h4>mocha --watch flag</h4>
<p>Rather than continuously going back to our console and running $ mocha, set the --watch flag so that mocha runs with any code change (on your test or SUT - system under test)</p>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ mocha -w
CALCULATOR
Add
✓ should add two numbers and return the total
✓ should throw an error if either value is not a number
2 passing (7ms)
</code></pre>
<small>If your production files are outside of the current working directory or your test files are not in the test directory, you can tell mocha where those files are after the -w flag.</small>
</section>
<section>
<h4>Creating specs for subtract</h4>
<pre><code class="hljs" data-trim contenteditable>
describe('Subtract', function() {
it('should subtract the second number from the first and return the result', function() {
var result = calc.subtract(2, 2);
expect(result).to.equal(0);
});
it('should throw an error if either value is not a number', function() {
var handler = function() {
calc.subtract('hey', 'now');
};
expect(handler).to.throw(Error);
expect(handler).to.throw('Invalid number');
});
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
CALCULATOR
Add
✓ should add two numbers and return the total
✓ should throw an error if either value is not a number
Subtract
1) should subtract the second number from the first and return the result
2) should throw an error if either value is not a number
2 passing (3ms)
2 failing
</code></pre>
</section>
<section>
<h4>Coding to make the Subtract tests pass (and improve code some)</h4>
<pre><code class="hljs" data-trim contenteditable>
var calc = {
checknum: function (num1, num2) {
if (typeof num1 !== 'number' || typeof num2 !== 'number') {
throw new Error('Invalid number');
}
},
subtract: function(num1, num2) {
this.checknum(num1, num2);
return num1 - num2;
}
</code></pre>
</section>
<section>
<h4>Going off the rails</h4>
<small>Let's add a function to our production calc without a test first <br>(yes, I know... Blaspheme! But, bare with me...)</small>
<pre><code class="hljs" data-trim contenteditable>
avg: function(nums) {
if(!Array.isArray(nums)) {
callback(new Error('Invalid array'));
return;
}
var sum = 0;
for (var i = 0; i < nums.length; i++) {
sum += parseInt( nums[i], 10 );
}
console.log(`avgSync() invoked: sum is ${sum}, count is ${nums.length}`);
return sum/nums.length;
}
</code></pre>
</section>
<section>
<h4>istanbul</h4>
<p>Istanbul gives us "coverage" reports that let us know stats and specifics about how much of our code is covered by our tests.</p>
<br>
<p>Homepage: <a href="http://gotwarlost.github.io/istanbul/">http://gotwarlost.github.io/istanbul/</a></p>
</section>
<section>
<h4>istanbul</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ sudo npm install -g istanbul
$ istanbul cover _mocha
</code></pre>
<img src="assets/istanbul01.png" alt="">
<img src="assets/istanbul02.png" alt="">
</section>
<section>
<h4>Coverage report tells us we are missing some tests!</h4>
<small>(After we review the coverage report...) Let's code the missing tests:</small>
<pre><code class="hljs" data-trim contenteditable>
describe('avg', function() {
it('should throw an error if the value passed is not an array of numbers', function() {
var handler = function() {
calc.avg('hey');
};
expect(handler).to.throw(Error);
expect(handler).to.throw('Invalid array');
});
it('should average an array of numbers', function() {
var result = calc.avg([3, 4, 5, 6, 7]);
expect(result).to.equal(5);
});
});
</code></pre>
</section>
<section>
<h4>Now, re-run istanbul</h4>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ istanbul cover _mocha
</code></pre>
<img src="assets/istanbul03.png" alt="">
<img src="assets/istanbul04.png" alt="">
</section>
<section>
<h4>Sinon</h4>
<ul>
<li>Homepage: http://sinonjs.org</li>
<li>Spy and Stub (and mocking) library for JavaScript</li>
<li>These tools help us in set up and isolate our unit tests by impersonating third party systems or components.</li>
<li>We can use spies in the assertion phase of the test and stubs in the set up phase.</li>
<li>We may have time to explore spies and stubs briefly.</li>
<li><a href="http://sinonjs.org/">http://sinonjs.org/</a></li>
<li><a href="http://sinonjs.org/docs/">Docs</a></li>
</ul>
</section>
<section>
<h4>Sinon Spy</h4>
<ul>
<li>A sinon spy is a function that records arguments, return value, the value of this and exception thrown (if any) for all its calls.</li>
<li>A sinon spy can be an anonymous function or it can wrap an existing function.</li>
<li>We can use Sinon Spies in place of real functions and they allow us to determine if the real function would have been invoked as we expect.</li>
</ul>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ npm install --save-dev sinon
</code></pre>
</section>
<section>
<h4>rewire</h4>
<ul>
<li><a href="https://www.npmjs.com/package/rewire">https://www.npmjs.com/package/rewire</a></li>
<li>With rewire, we can inject test variable data into our System Under Test (SUT) that can override other data or variables</li>
<li>Because we can inject variables, rewire allows us to replace real data with test data for unit tests</li>
</ul>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ npm install --save-dev rewire
</code></pre>
</section>
<section>
<h4>Sinon Spy / Rewire Example</h4>
<small>We can also combine sinon spies with rewire to overwrite object methods with spies</small>
<pre><code class="hljs" data-trim contenteditable style="background-color:#000000">
$ npm install --save-dev sinon rewire
</code></pre>
<pre><code class="hljs" data-trim contenteditable >
var sinon = require('sinon');
var rewire = require('rewire');
var calc = rewire('../lib/calc'); // require
describe('CALCULATOR', function() {
beforeEach(function(){
this.console = {
log: sinon.spy()
};
calc.__set__('console', this.console);
});
</code></pre>
<pre><code class="hljs" data-trim contenteditable >
it('should average an array of numbers', function() {
var result = calc.avg([3, 4, 5, 6, 7]);
expect(result).to.equal(5);
expect(this.console.log.callCount).to.equal(1); // add this line
});
</code></pre>
</section>
<section>
<h4>Async Tests</h4>
<small>If time, let's fumble through an example....</small>
<br><small>calc-spec.js:</small>
<pre><code class="hljs" data-trim contenteditable >
describe.only('avgAsync', function() { // note the 'only' inclusive selector
it('should average of an array asynchronously', function() {
calc.avgAsync([3,4,5,6,7], function(error, result) {
result.should.equal(555);
});
});
});
</code></pre>
<small>calc.js:</small>
<pre><code class="hljs" data-trim contenteditable >
avgAsync: function(nums, callback) {
setTimeout(function() {
var sum = 0;
for (var i = 0; i < nums.length; i++) {
sum += parseInt( nums[i], 10 );
}
callback(null, sum/nums.length);
}, 1000);
}
</code></pre>
</section>
<section data-transition="slide" data-background="#b5533c" data-background-transition="zoom">
<h4>Async Test: run mocha</h4>